Document FR-A-2.630.030 describes and represents a frame holder for prescription glasses of the type featuring two jaws mounted in such manner that they slide in relation to each other so that they can move toward or away from each other, and also featuring a device to center the frame between the jaws so as to hold said frame in a reference plane.
French patent application No. 91 09595 describes and represents an apparatus designed to automatically pick up the shape and/or profile of the inside contour of a glass frame rim using a frame holder with sliding jaws.
The execution of pairs of glasses according to an automated process requires indeed to be able to carry out accurately and automatically the edging of ophthalmic lenses with which glass frames are to be fitted, using a grinding machine in which the cutting operations are controlled by computerized data from the apparatus picking up the shape of the frame.
In such apparatus designed to pick up the shape of the frame, it is necessary to hold the glass frame in a highly precise and reliable manner during the plotting operations.
Under the known design of the above-mentioned frame holder, the user must show extreme skill to hold the frame basically in the reference plane while the sliding jaws are moved toward each other.
This applies for example to the device described in DE-A-41 26 313 by NIDECK CO. LTD. This prior document describes a cutting and polishing machine for ophthalmic lenses, featuring a device to determine the three-dimensional measurements of a glass frame so that these measurements, especially the measurement of the spacing of the geometric centers of the lenses, can be used to cut the lenses based on the dimensions of the frame of the glasses.
The glass frame is held through moving elements provided with holding pins and clamping elements so that the holding of the frame under this prior device involves a great number of moving parts and is highly complex.
Furthermore, as the elements extend toward the inside of the frame in the direction of the location of the lenses (FIG. 3), these elements are likely to hinder any possible plotting of the inside contour of a glass frame rim so that this device is not suitable for that measurement.
In addition, the device under the prior document does not feature any means to support the frame before its being clamped by the jaws.
The jaws must be moved close to the frame, which requires holding the frame by hand until it is fully gripped by the clamps on each side of the frame.
Any mishandling can either cause the frame to fall if it is improperly held, or to be inaccurately positioned in the frame holder, especially with respect to the geometrical reference plane.
Under various designs of apparatus intended to pick up the shape of the rim of a glass frame held between closed jaws, it is also necessary to run along the inside of the frame rim a sensor or tracer, which requires during the pick-up phase to completely free the inside of the frame rim.
The purpose of this invention is to propose a new design of frame holder permitting to eliminate the above-mentioned disadvantages.